St. Louis Downtown Airport to Boeing Fld/King County International CPS → BFI
1,496 nautical miles (1,722 statute miles) northwest on a straight line, true course 302°, about 302° magnetic at the departure end (variation 0E). At 120 knots that is 13 h 01 min at the quickest height in today's winds (18,000 ft, a 5-knot headwind), arriving about 5:30 pm PDT (00:30 UTC). Right now CPS is VFR, wind calm; BFI is VFR, wind calm. For planning, not a briefing: the legal preflight briefing comes from Flight Service (1-800-WX-BRIEF) or the FAA's own tools. Airlines fly this pair: 3 flights in the DOT's last twelve reported months, the route's page.
The route the straight line, the warnings crossed, restrictions, pilot reports and the airports along the way · click a mark for its words
Green, blue, red and purple airport dots are the flying conditions reported there now (VFR, marginal VFR, IFR, low IFR); grey means no report. Red areas are SIGMETs, orange areas AIRMETs, hatched red areas temporary flight restrictions. Map tiles: OpenFreeMap, data © OpenStreetMap contributors.
Warnings the route crosses SIGMETs and AIRMETs whose area the line passes through or comes within 25 nm of
- AIRMET TANGO 2W: low-level wind shear (due to air speed loss or gain of 20 knots or more below 2,000 ft above the ground). Over the route from 70 to 479 nm out.
- AIRMET SIERRA 4E: low cloud or poor visibility (IFR conditions) (due to ceilings below 1,000 ft, visibility below 3 miles, precipitation, mist). Over the route from 459 to 1157 nm out.
- AIRMET TANGO 1W: low-level wind shear (due to air speed loss or gain of 20 knots or more below 2,000 ft above the ground). Near the route, 738 nm along the route.
- AIRMET ZULU 2C: moderate icing up to 23,000 ft. Over the route from 798 to 958 nm out.
- AIRMET SIERRA 1E: mountains obscured by cloud (due to mountains obscured by clouds, precipitation, mist). Over the route from 848 to 1297 nm out.
- AIRMET ZULU 2C: moderate icing up to 18,000 ft. Over the route from 968 to 1317 nm out.
- AIRMET TANGO 1W: moderate turbulence above 18,000 ft from 18,000 ft to 39,000 ft. Over the route from 1157 to 1467 nm out.
A SIGMET warns of weather hazardous to all aircraft; an AIRMET of weather that matters to small aircraft and to flying without instruments. "From 60 to 180 nm out" is measured along the route from CPS.
Pilot reports along the route within 50 nm of the line, last three hours, the serious ones first
No pilot reports within 50 nautical miles of the line in the last three hours.
Winds aloft along the route, and the time en route the forecast for use 08:00–15:00 UTC · at 120 knots true airspeed
The westbound cruising heights for this course (VFR: even thousands plus 500 ft; above 18,000 ft the forecast levels), with the wind averaged along the line from the 15 forecast points nearest it (STL, COU, MKC, DSM, OMA, GRI, ONL, PIR, RAP, BIL, DLN, LWS, GEG, YKM, SEA). A plus sign is a headwind, a minus sign a tailwind.
| Height | Average wind | Head- or tailwind | Temperature | Ground speed | Time en route | Arrival |
|---|---|---|---|---|---|---|
| 4,500 ft | 250° at 18 kt | +13 kt | 17 °C | 107 kt | 13 h 59 min | 6:28 pm PDT (01:28 UTC) |
| 6,500 ft | 260° at 16 kt | +12 kt | 11 °C | 108 kt | 13 h 51 min | 6:20 pm PDT (01:20 UTC) |
| 8,500 ft | 250° at 13 kt | +9 kt | 6 °C | 111 kt | 13 h 29 min | 5:58 pm PDT (00:58 UTC) |
| 10,500 ft | 240° at 14 kt | +8 kt | 2 °C | 112 kt | 13 h 21 min | 5:50 pm PDT (00:50 UTC) |
| 12,500 ft | 240° at 15 kt | +8 kt | -1 °C | 112 kt | 13 h 21 min | 5:50 pm PDT (00:50 UTC) |
| 14,500 ft | 240° at 15 kt | +7 kt | -5 °C | 113 kt | 13 h 14 min | 5:43 pm PDT (00:43 UTC) |
| 16,500 ft | 230° at 14 kt | +6 kt | -9 °C | 114 kt | 13 h 07 min | 5:36 pm PDT (00:36 UTC) |
| 18,000 ft FL180 | 230° at 14 kt | +5 kt | -13 °C | 115 kt | 13 h 01 min | 5:30 pm PDT (00:30 UTC) |
| 24,000 ft FL240 | 230° at 25 kt | +9 kt | -24 °C | 111 kt | 13 h 29 min | 5:58 pm PDT (00:58 UTC) |
| 30,000 ft FL300 | 250° at 33 kt | +23 kt | -33 °C | 97 kt | 15 h 25 min | 7:54 pm PDT (02:54 UTC) |
| 34,000 ft FL340 | 250° at 38 kt | +26 kt | -38 °C | 94 kt | 15 h 55 min | 8:24 pm PDT (03:24 UTC) |
| 39,000 ft FL390 | 250° at 42 kt | +30 kt | -45 °C | 90 kt | 16 h 37 min | 9:06 pm PDT (04:06 UTC) |
Based on data from the 12th at 06:00 UTC; valid on the 12th at 12:00 UTC for use 08:00 to 15:00 UTC; temperatures above 24,000 ft are below zero. Heights are above sea level; a height is left out when the forecast has no wind for it over most of the line (the ground is higher). Ground speed is the airspeed less the headwind; the time en route is for the straight line and ignores climb, descent and routing around weather.
The forecast points as issued
| Point | From | 3,000 | 6,000 | 9,000 | 12,000 | 18,000 | 24,000 | 30,000 | 34,000 | 39,000 |
|---|---|---|---|---|---|---|---|---|---|---|
| STL | used from 0 nm out; 11 nm from the line | 250/26 | 240/21 15° | 240/22 11° | 250/23 6° | 270/28 -7° | 260/30 -19° | 280/52 -31° | 280/57 -40° | 300/57 -49° |
| COU | used from 50 nm out; 40 nm from the line | 250/36 | 260/14 16° | 250/5 12° | 260/12 6° | 260/24 -7° | 260/35 -19° | 280/58 -31° | 280/62 -40° | 290/60 -49° |
| MKC | used from 150 nm out; 78 nm from the line | 240/49 | 240/21 20° | 220/19 13° | 230/21 6° | 260/26 -7° | 250/37 -19° | 270/66 -31° | 270/65 -38° | 280/60 -48° |
| DSM | used from 200 nm out; 72 nm from the line | 250/47 | 260/25 20° | 240/19 11° | 240/31 5° | 250/26 -9° | 260/38 -20° | 260/47 -34° | 270/58 -37° | 270/61 -47° |
| OMA | used from 249 nm out; 38 nm from the line | 230/47 | 240/33 21° | 230/22 13° | 220/27 5° | 240/35 -8° | 250/43 -21° | 260/47 -33° | 260/59 -36° | 270/58 -46° |
| GRI | used from 349 nm out; 61 nm from the line | 230/39 23° | 230/32 15° | 210/29 7° | 230/31 -8° | 230/43 -21° | 250/52 -31° | 260/59 -35° | 260/59 -46° | |
| ONL | used from 399 nm out; 35 nm from the line | 250/31 22° | 230/27 16° | 220/25 8° | 230/25 -9° | 220/29 -22° | 250/42 -33° | 250/48 -36° | 250/52 -46° | |
| PIR | used from 549 nm out; 92 nm from the line | 230/15 15° | 220/22 14° | 220/24 6° | 200/32 -10° | 210/48 -22° | 240/45 -33° | 240/43 -37° | 250/55 -46° | |
| RAP | used from 599 nm out; 50 nm from the line | 250/28 16° | 260/31 10° | 240/25 4° | 210/35 -10° | 200/45 -23° | 230/47 -31° | 230/47 -36° | 230/51 -46° | |
| BIL | used from 798 nm out; 107 nm from the line | 300/14 | 270/19 -2° | 260/26 -2° | 220/28 -13° | 210/51 -25° | 220/56 -33° | 220/61 -39° | 220/72 -45° | |
| DLN | used from 998 nm out; 67 nm from the line | 190/10 -4° | 220/23 -4° | 210/21 -18° | 210/43 -28° | 210/60 -33° | 210/72 -37° | 210/67 -44° | ||
| LWS | used from 1147 nm out; 102 nm from the line | L/V | 340/5 -3° | L/V -6° | 040/7 -10° | 100/23 -22° | 180/30 -31° | 190/11 -34° | 200/11 -36° | 220/23 -40° |
| GEG | used from 1297 nm out; 44 nm from the line | 060/7 -2° | 070/12 -6° | 050/8 -8° | 120/11 -21° | 110/18 -33° | 030/22 -37° | 040/6 -38° | 240/7 -41° | |
| YKM | used from 1347 nm out; 63 nm from the line | 360/6 | 360/11 -1° | 030/20 -7° | 040/21 -11° | 020/55 -18° | 010/84 -26° | 010/79 -40° | 010/45 -42° | 350/23 -42° |
| SEA | used from 1447 nm out; 25 nm from the line | 350/5 | 010/6 0° | 010/9 -4° | 010/27 -6° | 010/51 -15° | 360/58 -26° | 360/60 -41° | 350/55 -48° | 340/30 -45° |
The weather now: both ends and the airports along the way public airports with a weather report within 25 nm of the line, one for each stretch
| Airport | Where | Conditions | Wind | Visibility | Ceiling | Elevation | Reported |
|---|---|---|---|---|---|---|---|
| CPS Cahokia/St Louis, IL | departure | VFR | calm | 8 mi | none | 412 ft | 5:53 am CDT (10:53 UTC) |
| SUS St Louis, MO | 20 nm out, 8 nm southwest of the line, tower | VFR | calm | 10+ mi | none | 463 ft | 10:54 UTC |
| ICL Clarinda, IA | 259 nm out, 1 nm southwest of the line | VFR | from the south-southwest (200°) at 9 knots, gusting to 16 | 10+ mi | none | 995 ft | 11:15 UTC |
| OMA Omaha, NE | 309 nm out, 12 nm north of the line, tower | VFR | from the south-southeast (150°) at 11 knots | 10+ mi | none | 984 ft | 10:52 UTC |
| ANW Ainsworth, NE | 509 nm out, 1 nm south of the line | low IFR Sky: overcast at 300 feet Weather: fog | from the north-northeast (020°) at 8 knots | 0.5 mi | 300 ft | 2,588 ft | 11:15 UTC |
| RAP Rapid City, SD | 668 nm out, 24 nm northeast of the line, tower | low IFR Sky: sky obscured at 200 feet Weather: fog | from the east-southeast (120°) at 7 knots | 0.25 mi | 200 ft | 3,203 ft | 10:52 UTC |
| SHR Sheridan, WY | 838 nm out, 3 nm north of the line | IFR Sky: a broken layer at 900 feet, overcast at 3,000 feet | from the northwest (310°) at 14 knots, gusting to 22 | 10+ mi | 900 ft | 4,021 ft | 11:11 UTC |
| BZN Bozeman, MT | 1028 nm out, 4 nm northeast of the line, tower | marginal VFR Sky: a few clouds at 1,200 feet, overcast at 2,300 feet | calm | 10+ mi | 2,300 ft | 4,473 ft | 11:24 UTC |
| BTM Butte, MT | 1087 nm out, 6 nm southeast of the line | IFR Sky: a broken layer at 600 feet, overcast at 2,000 feet | calm | 8 mi | 600 ft | 5,550 ft | 10:53 UTC |
| PUW Pullman/Moscow, WA | 1277 nm out, 6 nm southwest of the line | VFR Sky: overcast at 4,700 feet | calm | 10+ mi | 4,700 ft | 2,566 ft | 10:53 UTC |
| MWH Moses Lake, WA | 1377 nm out, 4 nm northeast of the line, tower | VFR | from the north-northwest (340°) at 6 knots | 10+ mi | none | 1,188 ft | 10:52 UTC |
| BFI Seattle, WA | destination | VFR | calm | 10+ mi | none | 21 ft | 3:53 am PDT (10:53 UTC) |
The highest airport on this list sits at 5,550 ft; the ground between airports is higher still. Check the sectional chart for the terrain and the minimum safe heights along the line.
At BFI when you get there the forecast at the estimated arrival, 5:30 pm PDT (00:30 UTC)
Wind from the west-northwest at 5 knots, visibility more than 6 miles, clear skies VFR
The whole forecast for BFI
- From Mon 5:00 am PDT (12:00 UTC): wind light and variable, visibility more than 6 miles, clear skies
- From Mon 12:00 pm PDT (19:00 UTC): wind from the west-southwest at 4 knots, visibility more than 6 miles, clear skies
- From Mon 2:00 pm PDT (21:00 UTC): wind from the west-northwest at 5 knots, visibility more than 6 miles, clear skies
- From Mon 8:00 pm PDT (03:00 UTC): wind calm, visibility more than 6 miles, scattered clouds at 25,000 feet
- From Tue 4:00 am PDT (11:00 UTC): wind from the south-southeast at 4 knots, visibility more than 6 miles, overcast at 10,000 feet
The forecast for CPS, the departure
- From Mon 7:00 am CDT (12:00 UTC): wind light and variable, visibility more than 6 miles, a few clouds at 25,000 feet
- From Mon 10:00 am CDT (15:00 UTC): wind from the southwest at 7 knots, visibility more than 6 miles, clear skies
Temporary flight restrictions on the line or within 25 nm of it
- 6/7634 CENTRALIA, MO, Monday, October 12, 2026 UTC 18 nm from the route, 100 nm along the route · a hazard on the ground (fire-fighting, a chemical spill, rescue work) · today · ZKC
- 6/8927 Kalispell, MT, Wednesday, October 14, 2026 through Wednesday, October 14, 2026 Local 5 nm from the route, 1157 nm along the route · a VIP movement · starts Wednesday 14 October · ZSE
- 6/8923 Kalispell, MT, Wednesday, October 14, 2026 through Wednesday, October 14, 2026 Local 5 nm from the route, 1157 nm along the route · a VIP movement · starts Wednesday 14 October · ZLC
Daylight
Sunset at CPS 6:27 pm CDT (23:27 UTC), at BFI 6:25 pm PDT (01:25 UTC) (civil twilight ends 6:56 pm PDT (01:56 UTC)).
Each restriction opens the FAA's own page with the exact area, heights and times. Ordinary notices to air missions (closed runways, lights out) are not shown: the FAA's notice search is not open to sites like this one at this time.
Radar and forecast charts for the regions crossed government pictures, the latest each time the page loads
Sources: the Aviation Weather Center's data service (SIGMETs, AIRMETs, graphical AIRMETs, pilot reports, winds and temperatures aloft, observations and terminal forecasts), the National Weather Service radar, the Weather Prediction Center's charts, the FAA's temporary flight restriction list and shapes, and the FAA's airport file for the positions, elevations and magnetic variation. Fetched when the page is viewed and kept a few minutes. Each leg is the straight line between its two airports; airways, terrain and airspace are not considered. The airports in detail: St. Louis Downtown Airport, Boeing Fld/King County International.